Facebook debugger alternative: test your link previews instantly
Facebook's official Sharing Debugger is slow, rate-limited, and requires a Facebook developer account. This free alternative replicates exactly what facebookexternalhit does: a real HTTP request with Facebook's user-agent, revealing the raw HTML and Open Graph tags Facebook reads when someone shares your link.
The same crawler powers link previews across Facebook, Messenger, and Instagram - together over three billion monthly users. If your og:title, og:description, or og:image tags are injected client-side by a JavaScript framework, Facebook sees nothing and your shared links look broken.
Paste a URL below to see what Facebook actually receives from your page.
How to use this tool
- 1
Choose a crawler from the list below (or select one from the category tabs)
- 2
Enter your page URL in the input field
- 3
Click 'Simulate crawl' to fetch your page with that bot's user agent
- 4
Review the HTML response - check for your page title, main content, and meta tags
- 5
Test multiple crawlers to compare how each one sees your site
How it works
When you select a crawler and enter a URL, we send a server-side HTTP request using that bot's exact User-Agent string. For example, selecting Googlebot sends the request with 'Mozilla/5.0 (compatible; Googlebot/2.1)' - the same identifier Google's real crawler uses.
Your web server receives this request and responds based on the User-Agent. If you have dynamic rendering, cloaking rules, or bot-specific logic configured, the response will reflect that. This is exactly what happens during a real crawl - we are replicating the full request/response cycle.
The returned HTML is then analysed for SEO elements: title tag, meta description, Open Graph tags, heading structure, canonical URL, structured data, and overall text content. Each element is scored, and the tool flags missing or problematic items with severity ratings.
When you select multiple crawlers, each one makes an independent request in parallel. The results are displayed side by side in a comparison table so you can spot differences - for example, a page that returns complete HTML for Googlebot but an empty shell for GPTBot.
Understanding Facebook (facebookexternalhit)
When someone shares a link on Facebook, Messenger, or Instagram, Facebook's crawler (facebookexternalhit) fetches your page to generate a link preview card. This card shows a title, description, and image pulled from your Open Graph (OG) meta tags in the raw HTML.
Facebook's crawler does not execute JavaScript. If your OG tags are injected client-side by React, Vue, or another framework, Facebook sees an empty page and generates either a generic preview with no image or no preview at all. This dramatically reduces engagement on shared links.
The impact of broken link previews extends beyond Facebook. Links shared in Messenger (which has over a billion users) and Instagram link stickers also use the same crawler. A missing or broken preview means fewer clicks, less engagement, and lower reach for your shared content.
Pre-rendering ensures that Facebook's crawler receives fully-formed HTML with all OG tags present, resulting in rich, visually appealing link previews that drive engagement and clicks.
Frequently asked questions
Why does my Facebook link preview show no image?▾
Facebook's crawler reads OG tags from raw HTML only. If your og:image tag is injected by JavaScript after page load, Facebook cannot see it. Use this tool to check whether your OG tags are present in the raw HTML response.
How do I force Facebook to refresh my link preview?▾
Use Facebook's Sharing Debugger tool (developers.facebook.com/tools/debug) to scrape your URL again. If your OG tags are still missing from the raw HTML, the preview will remain broken until you fix the underlying issue with pre-rendering or server-side rendering.
Does fixing Facebook previews also fix Instagram?▾
Yes. Instagram, Facebook, and Messenger all use the same crawler (facebookexternalhit) to generate link previews. Fixing your OG tags for Facebook automatically fixes them for all Meta platforms.
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Preview your link as it appears in WhatsApp messages. WhatsApp uses Facebook's crawler infrastructure and does not execute JavaScript. Missing OG tags mean no thumbnail, no title, and no description in chat.
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